Control system for pump cycling

ABSTRACT

A filter unit using a bump-type filter is disclosed. Briefly stated, a chamber has a fluid inlet conduit so that contaminated fluid, upon entering the chamber, is directed upwardly towards filter tubes and downwardly towards the bottom of the chamber. The fluid flow is diverted during startup so as to be directed only downward. A bump handle is disposed between two fluid outlet conduits such that one is opened and the other is closed and the reverse when the bump handle is in a first or second corresponding position. A plurality of microswitches are utilized so that the pump is not enabled during bumping or when a dump valve is open, but is enabled during system operation or startup.

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to U.S. application Ser. No. 07/141,651, which is now U.S. Pat. No. 4,872,981, issued Oct. 10, 1989, entitled "Split Inlet for Filter" filed concurrently herewith.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates, generally, to a filter wherein a tank casing is divided by tube sheet into lower and upper chambers that have respectively an inlet for fluid to be filtered and outlet for the filtered fluid, and more particularly to a control system for a filter in which system startup, operation and backwashing are interlocked in order to prevent erroneous operation.

2. Description of the Prior Art

It is known in the art to utilize filters of the pressure type wherein a pressure differential in the liquid being filtered is maintained at opposite sides of a filtering element. Such filters typically use filter elements formed of porous or finely perforated tubes. Uses of such filters are typically for filtering dry cleaning solvents and the like. The operation of such filters is relatively simple. Filtering is usually accomplished by a diatomaceous earth in suspension, with the solvent to be filtered being forced through filter tubes thereby reducing the size of the interstices or perforations in the tube wall and thus enhancing filter operation, such as the removal of lint and dirt from the solvent.

Cleaning of these types of filters is, in concept, quite simple. Generally, the fluid flow is stopped with the result that the diatomaceous earth is allowed to fall to the bottom of the container and settle since it is generally heavier than the solvent. Thereafter, the filtered material may be drained off. Contemporaneously with the cessation of fluid movement is the shaking of the filters known as "bumping". This is generally accomplished by mounting the filter elements on a plate which may be moved while still in the vessel. By moving the plate which holds the filter elements, and striking it abruptly against a barrier or stop, the remaining particles of diatomaceous earth and filtered matter are shaken off the filter elements and hence the use of the word "bumping". Immediately prior to bumping of the filter, backwashing may be accomplished in order to further dislodge matter from the filters. An example of this may be found in U.S. Pat. No. 3,100,190 "Pressure Filter and Filter Tube Therefor" issued Aug. 6, 1963 to R. B. Hobson, Jr. A related disclosure may also be found in U.S. Pat. No. 3,642,141 "Filter Tube and Connection Thereof to Tube Sheet" issued Feb. 15, 1972, to Hobson, Jr. Both of these patents are specifically incorporated by reference herein. These references disclose bump-type filters and are particularly drawn to the filter element therein.

Moreover, these references utilize a fluid inlet wherein the incoming liquid picks the filter medium, such as diatomaceous earth, up off the floor of the container so as to deposit it, or redeposit it, on the filter tube's exterior surfaces in order to perform its filtering function. This is accomplished by use of an elbow on the inlet pipe looking downward toward the bottom of the container. The fluid stream therefore hits the floor and stirs the accumulated solids into a suspension. In large filters, the flow can be so great that the filter tubes themselves are disturbed by the turbulence (e.g. 2000 gpm in a 60 inch diameter unit). Further, since the bottom ends of the tubes are not anchored in any way, the turbulence can "hammer" the tubes, causing interstitial squirming. The filtering material and/or dirt may also be forced to slide through to the clean side and go downstream into the process thereby defeating the entire purpose of the filter.

Also, filter systems were designed so as to be automated in order to facilitate cleaning of the filters. Such automation typically included a myriad of control devices, timers, solenoids, air valves, air cylinders and the like. While all of these help to ensure proper filter element cleaning, there are a significant number of drawbacks. Such drawbacks include the high cost of design, installation and repair, as well as the complexity in understanding how the system works. Further, since no two applications are alike due to variances in materials to be filtered out, use and the like, each system had to in effect be individually designed and individually "tuned" to the particular application. This therefore led to automated systems which still had to be constantly watched and adjusted.

Further, any maintenance which has to be performed must be done by one who is skilled not only in filters of this type but to particular applications and, in some situations, to individual systems. Also, the systems were generally not amenable to manual override situations since cleaning the filter in the wrong sequence could cause operational damage to the pumps, or filters and the like. This would result in a situation such as, for example, where the tubes are in a bump-type mode and therefore loose but the fluid pump is either left on or inadvertantly turned on. Another problem existed where all inlet and outlet valves were closed and yet the pump was left on or, just as serious, where the fluid dump outlet is left open and the pump is left on, thereby spilling solvent and filter mediums such as diatomaceous earth and the filtered material.

SUMMARY OF THE INVENTION

It is an object of the present invention to produce a filter which is relatively free of complex automatic control systems. It is a further object of the present invention to produce a filter which does not have to be individually engineered for each and every application site. It is a further object of the present invention to produce a filter which is relatively inexpensive to manufacture and install. A still further object of the present invention is to produce a filter which is simple to operate and does not require "skilled" labor to maintain.

A further object of the present invention is to produce a filter wherein the fluid inlet is controllable so that turbulence does not damage or otherwise negatively affect the performance of the filter tubes. A still further object of the present invention is to produce a fluid inlet which eliminates interstitial squirming and eliminates the migration of dirt and material to the cleaned fluid side of the filter. A still further object of the present invention is to produce a device which provides interlocking elements which prohibit certain portions of the filter element from operating while other steps are being performed. Such interlocking includes operation of the filter or a pump while a dump outlet is open. Further interlocking would include the prohibition of filter operation while the filter tubes are in the "bump" position and therefore subject to undesirable movement.

Yet another object of the present invention is to produce a device wherein the clean fluid outlet conduit acts as a pressure-relief valve. It is still a further object of the present invention to produce a filter device wherein at least two clean fluid outlet conduits are utilized and wherein at least one of the conduits acts as a pressure-relief valve should the conduit being utilized become blocked. It is yet another object of the present invention to produce a filter of the type described which may be retrofitted to substantially all similar units presently existing in the field.

A still further object of the present invention is to produce a filter for filtering fluid flowing therethrough which comprises a casing, a tube sheet which divides the casing into a filtered and an unfiltered chamber and has openings therethrough, a handle external to the casing and disposable between a first position that permits vertical movement of the tube sheet and a second position that prohibits such vertical movement, a sensor to determine the position of the handle for permitting and prohibiting the fluid flow through the filter, a filter unit in each opening in the tube sheet, at least two fluid outlets in the filtered chamber which are interconnected so that at least one fluid outlet is closed when the remaining fluid outlet is open, and a fluid inlet means in the unfiltered chamber.

DESCRIPTION OF THE DRAWINGS

Reference may be now had to the accompanying drawings in which;

FIG. 1 is an elevational view of the exterior and interior portions of the chamber of the present invention;

FIG. 2 is a diagrammatic cross-sectional view taken through the upper portion of the chamber of the present invention;

FIG. 3 is a block diagram illustrating in flow chart format, operation of the present device;

FIG. 4 is a perspective elevational view of the present invention;

FIG. 5 is a top view of the horizontal control plate of the present invention; and

FIG. 6 is a diagrammatic cross-sectional view of the chamber of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Construction

Referring now to FIG. 1, there is shown a partial cross-sectional elevational vie of the housing of the present invention. Shown is filter unit 10 which is generally comprised of chamber 12 and lid 14. The chamber 12 is preferably of corrosion resistant steel, although other suitable materials may be utilized. Disposed at the lower end of the chamber 12 is a fluid inlet conduit 16 which enters the side of the chamber 12 and terminates at a split inlet to form a "T" 18. The split inlet "T" diverges into an upper inlet conduit 20 and a lower inlet conduit 22. Valve disk 24 is disposable between upper inlet conduit 20 and lower inlet conduit 22 at the desired suitable height as will be discussed more fully below. Contaminated or dirty fluid or solvent 26 enters fluid inlet conduit 16 and upon entering inlet "T" 18 is diverted upwardly through upper inlet conduit 20 or downwardly through lower inlet conduit 22 as determined by the position of valve disk 24. The position of valve disk 24 is controlled by control shaft 25 which exits through the bottom of conical section 66 of chamber 12. Control shaft 25 may be a threaded rod so as to vary the height of valve disk 24 or may be part of a slide mechanism (not shown) as desired.

Upper inlet conduit 20 terminates at the bottom of lower tube sheet 30. Accordingly, contaminated fluid 26 moving through upper inlet conduit 20 is forced into the space between upper tube sheet 28 and lower tube sheet 30. Upper filter tube 32 is connected to upper tube sheet 28 as shown and extends through lower tube sheet 30. Upper filter tube 32 is loosely fitted through the associated aperture in lower tube sheet 30. Lower filter tube 34 is secured to upper filter tube 32. Therefore, contaminated fluid passing through inlet conduit 20 is forced between upper and lower tube sheets 28,30 respectively and is forced to escape through space 33 (FIG. 2) between upper filter tube 32 and lower tube sheet 30. This therefore causes the contaminated fluid 26 to enter the chamber 12 in a downward direction.

In the preferred embodiment of the present invention, upper filter tube 32 is a mesh having shrink wrap thereon. Lower filter tube 34 is attached to upper filter tube 32 just at the termination of the shrink wrap. Therefore, unfiltered fluid 26 must pass through upper and lower tube sheets 28,30 and enters the main part of chamber 12 via space 33 at the intersection of upper filter tube 32 and lower tube sheet 30. Accordingly, unfiltered fluid 26 is caused to flow downward in chamber 12. Filtered fluid 41 would pass through lower filter tube 34, up through the center of upper filter tube 32 and hence upper tube sheet 28 and finally exit through first outlet conduit 36. It has been found that this downward movement of unfiltered fluid 26 has a number of significant advantages. One such advantage is that bridging between adjacent filter tubes of diatomaceous earth is eliminated. Further, a washing effect is accomplished which aids in preventing stratification of the filter media on the tubes. Additionally, undesirable turbulence which may cause interstitial squirming and/or damage to the tubes is no longer present. It is to be understood that upper filter tube 32 may be of any suitable material or configuration such as, for example, stainless steel which would provide support to lower filter tube 34 and would prevent the accumulation of filter media thereon as well as prevent the passage of unfiltered fluid from its exterior to its interior.

Contaminated fluid 26 is also, as mentioned, forced through lower inlet conduit 20 which terminates adjacent the bottom of conical section 66 of chamber 12. Thereafter contaminated fluid 26 is forced upward towards filter tubes 32,34.

Accordingly, contaminated fluid 26 is caused to enter the filter tube 34 from an upward and a downward direction. This therefore minimizes turbulence at the tubes themselves. The fluid then passes through the center of filter tubes 32,34 into lid 14 and thereafter first outlet conduit 36 or second outlet conduit 37. Clean or filtered fluid 41 is accordingly forced to enter fluid outlet intake 38 and thereafter exit conduit 40. First outlet valve disk 68 in conjunction with outlet valve spring 94 is used to enable or prohibit the passage of clean or filtered fluid 41 therethrough as described more fully below.

Slide rod 42 is movably disposed through collar 44 contained at the top of lid 14 and at the upper end is attached to ring 46 and at the lower end is attached to upper tube sheet 28. Accordingly, vertical movement of slide rod 42 will cause upper tube sheet 28 and therefore necessarily filter tubes 32,34 to move simultaneously therewith and will also cause movement of lower tube sheet 30 which is attached to upper tube sheet 28 (as shown more clearly in FIG. 6). Lid 14 has an upper flange 50 while chamber 12 has a lower flange 52 which is matable with upper flange 50. Bolts 48 are utilized to clamp together upper and lower flanges 50,52 respectively in order to form a liquidtight filter unit 10.

Disposed at the lower end of conical section 66 is fluid outlet conduit 54 having at one end outlet valve 56. Outlet valve 56 is controlled by lever 58 with microswitch 60 being adjacent thereto in order to determine the condition, i.e. opened or closed, of outlet valve 56. Fluid outlet conduit 54 is relative to aperture 62 in conical section 66. Legs 64 are used to support the filter unit 10.

In the preferred embodiment of the present invention, lower filter tube 32 is in fact medium-support device wherein filtering medium such as diatomaceous earth, normally in suspension in the solvent or fluid to be filtered, is deposited (or redeposited) on the exterior of lower filter tube 32, thus performing a filtering function. Accordingly, this type of filter, generally but inaccurately known as a precoat filter, is reusable a number of times simply by stopping the flow of fluid therethrough and allowing the diatomaceous earth to fall to the bottom of the chamber. Once the diatomaceous earth is completely saturated with contaminants, outlet valve 56 is opened thereby allowing the earth to be removed. New earth may be entered through the top of chamber 12, by removal of lid 14 but is normally introduced through fluid inlet conduit 16 during system startup.

Referring now to FIG. 2, there is shown a cross-sectional view taken through the upper or lid portion of the present invention showing greater detail of the structure therein. Clearly illustrated is how first and second outlet conduits 36,37 respectively are oriented so as to operate in alternating or opposite conditions. That is, for example, when outlet conduit 36 is opened so as to allow clean fluid 41 to exit chamber 12 and therefore pass therethrough, second outlet conduit 37 is closed. Each conduit 36,37 is in turn comprised of fluid outlet intake 38 and an exit conduit 40. First and second outlet valve disks 68,69 respectively control the position of stops or gates 82,83 thereby allowing or prohibiting the passage of fluid therethrough. Outlet valve spring 94 is disposed around valve disk 68,69 and is used for spring biasing stops 82,83 respectively. Disposed between disks 68,69 is pivoting bar 92 which is utilized for keeping one outlet conduit open and one outlet conduit closed (as shown more clearly in FIGS. 4 and 6). Pivoting bar 92 is retained valve disks 68,69 by wing nuts 84,85. Also disposed between valve disks 68,69 is stationary bar 96 which is retained in its position by nut 95 disposed around each valve disk 68,69 (as shown more clearly in FIGS. 4 and 6). Also shown is compression spring 86 which is disposed around slide rod 42 so as to pull vertically away from lid 14. Collar 44, in which slide rod 42 moves therethrough, is comprised of bore 88 and having a plurality of seats 90 therein. Seats 90 allow for appropriate gasketing thereby prohibiting the exiting of clean filtered fluid therethrough.

Apparent when viewing FIG. 2 is that the normally closed outlet conduit may, due to spring biasing by outlet valve spring 94, act as a pressure-relief valve should a blockage occur in the open outlet conduit. Additionally, it is possible to utilize both outlet conduits simultaneously or to eliminate an outlet conduit or similarly add a third or subsequent outlet conduits as desired.

Referring now to FIGS. 4 and 6, there is illustrated an elevational side view of the present invention. Shown is the filter unit 10 comprised of chamber 12 and lid 14 disposed thereon. Disposed on the exterior of chamber 12 is sight glass 122, which enables the operator to view the interior of filter unit 10. Bump handle 124 is connected between ring 46 of slide rod 42 and is attached by clamp 125 to stationary arm 96. Bump handle 124 is bent so as to be disposed in handle guide 126 (shown more clearly in FIG. 5). Handle guide 126 is formed of plate steel and has a left and right slot 136,138 respectively and a channel 140 disposed between slots 136 and 138. Bump handle 124 has attached to it retainer handle 128 which engages with a bore 42 disposed at either end of left and right slots 136,138. In this manner, bump handle 124 is "locked" into left or right slots 136, 138. Bump handle 124 is positioned so as to ride against pivoting bore 92. Therefore, when bump handle 124 is disposed in right slot 138, first outlet conduit 36 is in the open position and second outlet conduit 37 is in the closed position. Similarly, when bump handle 124 is disposed in left slot 136, second outlet conduit 37 is open while first outlet conduit 36 is closed. In this manner the alternating or reciprocating fashion of outlet conduits of 36,37 is accomplished. Disposed under handle guard 126 is bar 130 with bar 130 having disposed directly adjacent thereto bump handle microswitch 132. Microswitch 132 is disposed adjacent bar 130 such that the electrical contacts contained in microswitch 132 are in one orientation (preferably closed) when bump handle 124 is disposed fully in left or right slot 136,138 and in a second orientation (preferably open) when bump handle 124 is intermediate left and right slots 136,138 such as, for example, in channel 140. Microswitch 132 is interconnected with microswitch 60 such that operation of the filter unit, i.e. pump actuation (not shown) is discontinued when bump handle 124 is intermediate right or left slots 136,138 or outlet valve 56 is not fully closed. Channel 140 allows bump handle 124 to move therethrough such that slide rod 42 is allowed to move vertically up or down and thereby effect bumping of filter tubes 32,34 as described below and as seen in FIG. 6.

Operation

Reference may be now had to FIGS. 1, 2, 3, 4 and particularly 6 in order to clearly understand operation of the present invention. It should be remembered that prior to startup of the present device, the diatomaceous earth will have settled or have been deposited at the bottom of chamber 12. Therefore, a startup procedure must be utilized before actual filtering can be accomplished. It is advantageous that the diatomaceous earth be deposited onto filter tube 34 as expeditiously as possible and that a pressure differential be maintained between the interior of filter tube 34 and the exterior thereof. The pressure, of course, being greater than the interior pressure due to the flow of fluid therethrough. During startup, it is imperative that bump handle 124 be firmly maintained in either right or left slots 136,138 with its position being positively sensed by bump handle microswitch 132. Similarly, since microswitch 60 is, preferably, in series circuit relationship with microswitch 132, it is imperative that outlet valve handle 56 be closed. This therefore ensures that the first or second outlet conduit 36,37 are in the appropriate opened and closed positions respectively. Additionally, valve disk 24 is, preferably, moved by control shaft 25 so as to be in the uppermost position as shown in FIGS. 1 and 6. This therefore effectively prohibits or substantially diminishes the amount of fluid which may pass through upper inlet conduit 20. Therefore, all incoming contaminated fluid 26 must enter fluid inlet conduit 16 and, effectively, pass through lower inlet conduit 22. This forces all contaminated fluid 26 to force all the diatomaceous earth upward into suspension in the chamber 20 and enabling it to therefore be deposited onto filter tubes 30,32 as rapidly as possible.

During this initial startup, a substantial amount of contaminated fluid 26 will pass through the entire filter 10 and exit first outlet conduit 36. Since the diatomaceous earth has not been fully deposited onto filter tubes 32,34, it is evident that the fluid is initially unfiltered or still contaminated. Therefore, a bypass route (not shown) must be utilized to take the contaminated fluid exiting outlet conduit 36 and to feed it back into inlet conduit 16 (not shown). This procedure is continued until the diatomaceous earth has been completely deposited onto the filter tube 34 such that the effluent has cleared up. Thereafter, the bypass may be eliminated (through suitable valving, conduits and the like--not shown). Once the bypass has been removed, the filter unit may then be placed effectively onstream until the accumulation of the contaminants causes an increase in pressure and subsequent diminuation of flow in the clean filtered fluid 41.

Further, once initial precoating has been accomplished, control shaft 25 and hence valve disk 24 are moved downwards such that incoming contaminated or dirty fluid 26 is diverted upwardly into upper inlet conduit and downwardly into lower inlet conduit 22. This therefore prohibits excessive disturbance of diatomaceous earth in the bottom of chamber 12. This therefore has the desired effect of stabilizing filter tubes 32,34 and preventing excessive pressure due to turbulence upon them and to further prevent slipping of the diatomaceous earth from the filter tubes should any eddies in the turbulence or any other condition result in an area of lessened pressure or wearing away of the diatomaceous earth from the filter tubes 32,34. This movement of control shaft 25 may be either manual or automatic such as, for example, by pneumatic or mechanical means by interlocking operation of bump handle 124 therewith.

It has been found that for some large scale applications it may be desirable to provide a bifurcated flow in chamber 12. This is accomplished by moving valve disk 24 via control shaft 25 to an intermediate position between its uppermost and lowermost positions. Therefore, unfiltered fluid 26 will flow first downward through lower inlet conduit 22 before being directed upwards towards lower filter tube 34 and will similarly flow upward through upper inlet conduit 20 before being directed downwards towards lower filter tube 34. This will cause the fluid to flow towards lower filter tube 34 from two opposite directions which will have the tendency to cancel out any possible undesirable turbulence effect on filter tube 34 by creating a substantially constant, equal and perpendicular pressure on filter tube 34. Accordingly, maximum uniform deposition of diatomaceous earth will accumulate on the filter tubes while stratification and bridging will be prevented.

Once it has been determined that throughput has decreased or that the effluent is not as clean as desired, it becomes necessary to clean filter tubes 32,34. Accordingly, the pump may either be turned off or the numb handle 124 is merely moved intermediate left and right slots 136,138 such as in the vicinity of channel 140. Bump handle 124 is then lifted through channel 140 into the position shown by dashed lines 124'. This thereby causes upper and lower tube sheets 28,30 to move vertically downward in chamber 12 to the position shown by dashed lines 28',30' along with associated filter tubes 32,34. Bump handle 124 is then moved back so that pper tube sheets 28,30 and therefore filter tubes 32,34 are moved back up such that the four components 28-34 are bumped against an upper surface in chamber 12 thereby causing contaminants and diatomaceous earth to fall to the bottom of chamber 12. During bumping, upon downward movement of the slide rod 42, liquid is displaced to the area above tube sheets 30,32 with the result that upon vertical upward movement of slide rod 42, the liquid is forced backward through tube sheets 30,32 thereby accomplishing a violent and extremely effective, what may be described as hydraulic back-wash operation. It is to be understood, however, that in this operation the fluid does not move but rather the tube sheets and associated filter tubes 28,32 move relative to the liquid thereby simulating rapid movement of the liquid so as to cause a pressure differential across each of the tube sheets 28,30. It has been found that backwashing creates a significant force which may in fact damage the bump handle 124 should the operator attempt to bump the filter without first shutting off the pump. For example, a 24 inch filter running at 20 pounds would see a force of 9,000 pounds. Hence, it has been found that it is most important that microswitch 132 be used to sense when the filter is in the "bump" mode. This operation is repeated until the bumping causes as much filter media as possible to fall to the bottom of the chamber 12, all of which may be viewed through sight tube 122. It is to be understood that although bumping may be accomplished manually as described, it is possible for automated bumping to be accomplished by use of pneumatic cylinders, actuators and the like.

Further, the mechanical stops used during the bumping process as well as sudden stopping of the tube sheets will result in static bumping, which in conjunction with the mentioned hydraulic bumping has been found to be effective in removing filter media from the filter tubes.

Thereafter, the startup procedure previously mentioned would be initiated in order to precoat filter tube 34 just before startup and hence filtration. In the event that this bumping procedure does not adequately reduce pressure and improve flow, it is necessary to remove the diatomaceous earth via fluid outlet conduit 54 and that new diatomaceous earth be introduced, preferably in the bypass conduits during the startup procedure. It has been found that it is generally advantageous to have one outlet conduit such as 36 expressly used for the purpose of exiting clean or filtered fluid 41 while the remaining outlet conduit, preferably second outlet conduit 37, be used in bypass operation during filter startup. Therefore, after bumping and during initial startup, bump handle 124 would be disposed in left slot 136. As soon as appropriate precoating of the diatomaceous earth on filter tube 34 has been accomplished, bump handle 124 is moved over to right slot 138. In this manner, it is possible to eliminate rapid valve changes and the like since bump handle 124 accomplishes the initiation or cessation of the bypass operation.

Additionally, it has been found that if it is desired to more rapidly precoat filter tube 34, a second pump may be introduced on line for the purpose of bringing a greater flow or volume of fluid through fluid inlet conduit 16. This is preferably accomplished by use of an additional microswitch adjacent left slot 136. Therefore, during the bypass operation described when bump handle 124 is in left slot 136, the microswitch adjacent thereto would cause the second pump to be energized. The second pump would be deenergized, thereby returning all fluid to normal flow conditions when bump handle 124 is removed from the bypass position into the "run" condition by its movement in right slot 138.

Accordingly, operation of the present device is relatively simple and foolproof and may be completed by following the steps substantially shown in FIG. 3. Accordingly, in block 102 of step 1, "set valves" indicates that first or second outlet conduits 36,37 are respectively closed and opened. Next, in step 2 at block 104, the pump would be started by use of bump handle microswitch 132 being energized when bump handle 124 is placed into left slot 136. This would then start the precoat cycle and may be either manually or automatically timed as desired. It has been found that, for example in the filtering of dry cleaning fluids, a suitable time of one to six minutes in order to accomplish precoating is reasonable. Once it has been determined that suitable precoating has been accomplished, online operation is accomplished as indicated in step 4 blocks 108,110 by moving bump handle 124 from left slot 136 to right slot 138 thereby closing second outlet conduit 37 (block 110) and opening first outlet conduit 36 (block 108). The system is then left onstream to run and filter the fluid as desired. Thereafter, when it is determined that the fluid is no longer being properly filtered or there is a diminished flow of clean fluid, it is necessary to bump the filter. It has also been found that typical onstream operation is on-and-a-half to three hours before bumping is required. This may be timed automatically or manually initiated by the operator. Accordingly, as indicated in step 5 block 112, bump handle 124 is moved into the center position intermediate slots 136,138 thereby shutting off the pump since its position is sensed by bump handle microswitch 132 and the filter is then bumped as previously described. Thereafter, as indicated in step 6 block 114, the entire cycle is again repeated. In the event that flow is not improved or the contaminated filter is not adequately cleaned, then it comes necessary to dump and replace some or all of the diatomaceous earth as previously described.

Further, due to "modular" nature of filters presently utilized and the construction of the present invention, many elements of the present invention may be "retrofitted" to existing systems without the need for substantial modifications and may in fact be done, so as to incorporate some or all of the features of the present invention.

It is to be understood that many variations from the present invention may be practised without departing from the spirit and scope of the present invention. For example, a plurality of tube sheets may be utilized while the fluid inlet conduits may be oriented in a plurality of directions so as to direct, for example, three or more streams of incoming contaminated fluid down towards the bottom of the chamber. Also, a number of devices may be pneumatically or electrically operated such as the dump valve or the outlet conduits while different types of switches such as magnetic switches or proximity sensors may be utilized.

Having thus described the present invention in detail, it is to be understood that the foregoing description is not intended to limit the spirit and scope thereof. What is desired to be protected by Letters Patent is set forth in the appended claims. 

What is claimed is:
 1. A filter for filtering fluid flowing therethrough, comprising:a casing; at least one tube sheet dividing said casing into a lower chamber and an upper chamber and being vertically movable within said casing, said tube sheet having openings therethrough; a filter unit in each said opening in said tube sheet; at least one fluid outlet in said filtered chamber; fluid inlet means in said unfiltered chamber; tube sheet movement means external to said casing for moving said tube sheet, said means being disposable between at least a first position permitting said movement of said tube sheet and at least a second position prohibiting said movement of said tube sheet; and sensor means to determine the position o said movement means, for respectively prohibiting and permitting fluid flow through said filter when said movement means is respectively in said first and said second position.
 2. A fluid according to claim 1, further comprising a second fluid outlet, disposed in said unfiltered chamber, for permitting the removal of fluid in said unfiltered chamber.
 3. A fluid filter according to claim 2, wherein said second fluid outlet in said unfiltered chamber is comprised of a conduit and a valve, said valve being disposable between an open position and a closed position for permitting and prohibiting respectively the flow of fluid therethrough, and further comprising a second sensor means proximate said valve for determining when said valve is in said open position and said closed position, for respectively prohibiting and permitting fluid flow through said filter when said valve is respectively in said open and said closed position.
 4. A fluid filter according to claim 3, wherein said fluid outlets are comprised of spring-biased pressure relief valves, said valves disposable between an open position for permitting the unencumbered flow of fluid therethrough, and a second position for permitting the flow of fluid therethrough when pressure exerted by the fluid exceeds a predetermined level.
 5. A fluid filter according to claim 1, wherein said at least two fluid outlets are disposed in said filtered chamber said fluid outlets in coaction when at least one fluid outlet is open.
 6. A filter fluid according to claim 1, further comprising a bracket means rigidly affixed to said casing for permitting the prohibiting movement of said tube sheet movement means, and wherein said sensor means is rigidly affixed to said bracket means. 